The present disclosure relates to the protecting of nozzles 100 or a nozzle area 102 on a micro-fluid ejection head 104. A schematic depiction is shown in FIG. 1. A major problem in maintaining a robust seal on such a device is the highly demanding and sometimes conflicting requirements for such an application. For example, the sealant material must coat the nozzles, thereby preventing fluid from leaking out of the nozzles for the entire “shelf life” of the ejection head. In addition, the sealant must be compatible with the fluid contained within the ejection head. Ideally, the sealant should not alter the properties of the fluid and it should not dissolve or appreciably swell when in contact with the fluid. The fluid should also not interfere with the ability of the sealant material to adhere to the surface of the ejection head. The sealant should also provide a physical barrier that not only prevents intermixing and/or contamination with other fluids and/or the external environment, it should prevent evaporation of any volatile components within the fluid. Also, the sealant should remove cleanly from the ejection head leaving a minimum amount of residue on the ejection head and nozzles so as to not affect the subsequent print (via misdirection or missing droplets on the page, for example). Conventionally, the primary sealant material has been an acrylate-based pressure sensitive adhesive (“PSA”) tape 106, an example of which is shown in FIG. 1. However, as the size of the ejection head nozzles has decreased and the complexity of the fluid components has grown with each new generation of printers, the ability of a PSA tape 16 to meet these application requirements has diminished drastically.
To better understand where the challenge lies in using a PSA tape for this type of application, it is necessary to describe how a PSA tape works. An example of a PSA tape is provided in U.S. Pat. No. 4,181,752. Typically, PSA tapes are copolymers of a major proportion of alkyl esters of acrylic acid (the alkyl group containing from about four to fourteen carbon atoms) and a minor proportion of at least one “modifying monomer” (also referred to as an adhesion promoter) such as acrylic acid, methacrylic acid, acrylamide, acrylonitrile, methacrylonitrile, N-vinyl pyrrolidinone, maleic anhydride, or itaconic acid. This type of copolymer is effective as a tape due to the soft nature of the polymer which enables efficient and rapid “wetting” of the substrate. Efficient coverage, or wetting, also maximizes surface area coverage and/or interaction between the adhesive tape and substrate. As the degree of coverage increases, the strength of the bond between the two surfaces increases. It is also a common practice to add multifunctional reactants (such as trimethylolpropane triacrylate) during the polymerization of these acrylate and “modifying” monomers. These multifunctional reactants act as crosslinking agents during the polymerization of these adhesive tapes, thereby increasing the molecular weight and cohesive strength of the resulting adhesive tape.
From a practical perspective, PSA tapes are classified based on two basic properties: compliance (the ability of the tape to conform to a substrate being adhered to) and cohesive strength (the ability of the tape to resist deformation under load). Compliance comes from the soft nature (low Tg) of the polymer in the adhesive tape while the cohesive strength arises from the chemical makeup, crosslink density, and molecular weight of the adhesive tape. However, these two properties are generally opposed to one another. For example, if a tape is too firm (resulting from a high crosslink density), its ability to “wet” or comply with the surface being bonded will be lacking. On the other hand, if a tape is too compliant, it will lack the strength necessary to maintain the bond under an applied load. Therefore, a delicate balance is always present when designing a tape for a specific application.
For the case of sealing a micro-fluid ejection head, maintaining an acceptable balance of compliance and cohesive strength has proven to be very difficult. It is now commonly observed that a PSA tape, which is sufficiently compliant to seal a micro-fluid ejection head, typically does not remove cleanly due to a lack of cohesive strength. The exact opposite case has been equally problematic; namely, adhesive tapes that have sufficient cohesive strength (for clean removal) typically do not seal the ejection head due to their lack of compliance. However, since both aspects are equally vital for the overall functional performance of a micro-fluid ejection head sealant, a compromise between these two properties is not an option. Therefore, it has become necessary to investigate more robust sealing options. Such an option is presented in the present disclosure.
In accordance with the disclosure, there is disclosed a reactant mixture suitable for sealing a micro-fluid ejection head comprising a vinyl-containing oligomer, a filler, and optionally a reactive diluent, and/or a photoinitiator.
Another embodiment comprises a method of protecting a nozzle area containing nozzles on a micro-fluid ejection head with a removable cured member comprising applying a reactant mixture to a nozzle area containing nozzles on a micro-fluid ejection head and exposing the reactant mixture to radiation to provide a removable cured member. The method may further comprise removing the removable cured member from the nozzle area. The method may also further comprise attaching a removal member to the nozzle area.
Another embodiment comprises a micro-fluid ejection head having nozzles sealed by a removable radiation cured member, wherein the removable radiation cured member comprises the reaction product of a vinyl-containing oligomer, a filler, and optionally a reactive diluent, and/or a photoinitiator.
Additional objects and advantages of the disclosure will be set forth in part in the description which follows, and/or can be learned by practice of the disclosure. The objects and advantages of the disclosure will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.
It is to be understood that both the foregoing general description and the following detailed description and figures are exemplary and explanatory only and are not restrictive of the disclosure, as claimed.